Proxy Mobile IP (PMIP) is a protocol that provides access and mobility capabilities to a terminal without the need for the terminal to support specific mobility related signaling. Mobility features are solely supported by a PMIP network. PMIP defines for the terminal a proxy care-of address (pCoA) that is sent by PMIP nodes towards an agent that owns a subscription for the terminal. The pCoA is the address of a gateway that provides connectivity to the terminal. A description of PMIP is made in RFC 5213, entitled “Proxy Mobile IPv6”, from the Internet Engineering Task Force (IETF).
The PMIP network comprises a local mobility anchor (LMA), sometimes called local mobility agent, and one or more media access gateways (MAG), which are also sometimes referred to as proxy mobile agents. The LMA and MAGs provide PMIP support to terminals. A terminal that is currently located within the PMIP network is provided access by one of the MAGs.
When a given terminal attaches to a domain that supports PMIP, it sends an access request, which arrives at a MAG, either directly or through an access point. The MAG sends information about the access request to the LMA in a Proxy Binding Update (PBU) message. The access request may also be forwarded from the MAG to an authentication server for authentication and profile retrieval. The PBU comprises an address of the MAG, called proxy care-of address (pCoA), to be used as a care-of address of the terminal. The LMA stores in a binding cache the pCoA with a home network prefix (HNP) of the terminal. This HNP, which is a form of subnet prefix, may be assigned to the terminal by the LMA. Sometimes, the LMA may obtain the HNP from a dynamic host control protocol (DHCP) server. The LMA replies to the MAG with a proxy binding acknowledgement (PBA) message carrying the HNP of the terminal. Having received the PBA, the MAG advertises the HNP on a link to the terminal. This makes the terminal act as if it was connected on a home link. The terminal configures for itself a home address (HoA) based on the HNP and on an interface identifier (IID) for an interface used to connect the terminal to the MAG. The IID may be supplied to the terminal by the LMA and sent via the MAG in the PBA message. The IID may alternatively be generated by the MAG itself. Whether the IID originates from the LMA or from the MAG, the MAG may advertise it along with advertising of the HNP. In other cases, the terminal may select its own IID. Any data traffic initiated at an external correspondent, intended to be sent to the terminal, is addressed to the HoA of the terminal. As the LMA is the entity that advertises the HNP beyond the PMIP network, it intercepts a packet of the data traffic and encapsulates and tunnels it to the MAG by use of the pCoA. The MAG receives this packet, decapsulates it, and sends it to the terminal. Packets originating from the terminal are sent through the MAG to the LMA and then to their destination addresses.
The operator of a PMIP network may at once support several access technologies. Because a specific MAG may be associated with an access point dedicated to one specific access technology, the operator may install, in close proximity of each other, a plurality of MAGs, each of which has distinct characteristics.
Today's terminals may support multiple concurrent functions and may comprise multiple access ports using multiple access channels, sometimes using distinct access technologies, for supporting these concurrent functions. A given terminal may, for example, use a wireless local area network (WLAN) radio access technology to connect through a first MAG towards a first correspondent node. The same terminal may at the same time use a cellular radio access technology, such as for example high speed packet access (HSPA), to connect with a second correspondent node through a second MAG. The terminal may further connect, for example, via the first MAG, towards the first and a third correspondent node. In such a case, the terminal will have two data flows established through the same first MAG for communicating with the first and third correspondent nodes. For the two data flows established through the first MAG, the LMA may allocate two distinct HNPs for the terminal, which leads to the assignment of two distinct HoAs to the terminal. Alternatively, a single HoA may be used to support more than one data flow, inasmuch as flow identities, inserted in each packet of each data flow, are used to distinguish the data flows.
When the terminal is concurrently connected through two MAGs, the terminal concurrently operates under two distinct HoAs. Two HoAs are used because the LMA has allocated distinct HNPs for use on these two MAGs and further because each of these connections is made through a distinct interface of the terminal, each interface having assigned thereto its own IID. In communicating with the correspondent nodes, the terminal uses these two distinct HoAs which are used as destination addresses by the correspondent nodes for sending packets towards the terminal. Of course, if the terminal is connected towards two correspondent nodes via the first MAG and towards another correspondent node via the second MAG, the two data flows that travel via the first MAG may still share the same HoA if the first MAG has not configured two distinct HoAs on the same link.
Current wireless access technologies allow moving a terminal between access points. One example of this may be when the terminal is located within the coverage of a WLAN network. Because such a network generally has limited geographical coverage, as a user of the terminal moves away from that coverage, it may be required to disconnect the terminal from a MAG associated with the WLAN network and to reconnect the terminal to another MAG associated with a cellular coverage.
Quality of a connection might provide reasons for moving a data flow from a first MAG to a second MAG. The terminal may for example detect that an available bandwidth on the first MAG is not sufficient for adequately supporting a service; this may happen for example on a WLAN connection used in a high traffic area. The terminal may elect to move a connection to the second MAG if that MAG provides a higher bandwidth, for example by use of HSPA. Other considerations for moving the data flow could be based on experienced or expected delays, or various quality of service (QoS) aspects. Of course, such decisions to move a connection could also be taken in a policy decision function within the PMIP network, for example for purposes of balancing a load between MAGs. When the terminal is connected towards two correspondent nodes through a same MAG, a decision of moving a connection from a first MAG to a second MAG because of QoS, load balancing, bandwidth or delay considerations may be applicable to a data flow linking the terminal to one of those correspondent nodes and not to another data flow linking the terminal to the other correspondent node. This may be the case, for example, when a higher QoS offered on the second MAG is available at a higher tariff for the user of the terminal.
Generally, from the standpoint of a given correspondent node, the HoA of the terminal, which is used as a source or destination address for communicating with the correspondent node, defines a session therebetween. If the HoA changes, for example because an interface has changed, the correspondent node understands that there has been a connectivity loss and that the session must be terminated. The correspondent node may initiate setting up a new session or it may simply abandon the session, expecting that the terminal will initiate a new session.